Diploid expression and translational regulation of rat acrosin gene.

Acrosin, a sperm acrosomal serine protease has been implicated in the recognition, binding and penetration of the zona pellucida of the ovum. Biosynthesis of acrosin was found to start in early round spermatids which are haploid germ cells. Here, we report that acrosin gene transcription occurs as early as at day 19 of rat spermatogenesis which contains diploid but not haploid spermatogenic cells. Translational control of the acrosin gene may be due to cytoplasmic protein factors which through RNA-bandshift experiments were found to bind to the 5'UTR of the acrosin mRNA. In order to differentiate between diploid and haploid spermatogenic cells at the molecular level, transcription of the protamine 2 gene during rat testicular development was evaluated. Protamine 2 transcripts could be demonstrated for the first time in 25-day-old testes which contain diploid as well as haploid spermatogenic cells.